The following products of eicosatetraenoic and eicosatrienoic acid metabolism: PGE2, PGE1, PGF2 alpha, PGF1 alpha, PGD2, TXB2 and hydroxyeicosatetraenoic acid, will be measured in media of cells incubating in the presence and absence of potential stimulators and inhibitors of prostaglandin biosynthesis. With these data, identification of the biochemical step being affected, phospholipase, cyclooxygenase, lipoxygenase, prostacyclin synthetase, thromboxane synthetase, or prostaglandin synthetase, may be possible. Several cells will be cultured; they include kidney cells (MDCK), bovine aorta endothelial cells, murine mononuclear cells (WEHI-5), rabbit aorta smooth muscle cells (R-I), rat type II alveolar epithelial cells (L-2) and human skin fibroblasts (D-550). The stimulators will include Vitamin A analogs, growth factors, steroids, microtubule binding drugs and catecholamines; the inhibitors will include mepacrin, indomethacin, imidazole and Vitamin E analogs. Stimulation or inhibition of biosynthesis will be monitored by radioimmunoassay of the conditioned media or radioimmunoassay after extraction of the conditioned media by XAD-2 and separation by hplc. With some cells, intracellular levels of cAMP will be determined and the levels correlated with stimulation or inhibition of prostaglandin biosynthesis.